I can successfully ping the machine either as "ping sa" or "ping 10.11.12.17", but the IP address and host do not appear in the drop down when attempting to create a TCP listener using the SQL Central Listener wizard:

There's no need to "setup a TCP/IP listener" for SQL Anywhere other than using the DBSRV17 executable (the networt server) - it uses TCP/IP by default, and as Ian has answered on your other question, defaults to use port 2638 if available or the first available "ephemeral port" (49152 or above).

My first guess is you are starting a personal server (dbeng17). For connections from other machines, you need a network server (dbsrv17). I believe you need a different license to use a network server than a personal server.

I don't know SQL*Plus but SQL Anywhere comes with Interactive SQL (DBISQL) as a graphical SQL query tool (also available within SQL Central), and there's an older dbisqlc utility with reduced functionality and minimal resource needs. Both do not offer a classic "command line interface" but allow the interactive execution of SQL commands, so DBISQL should certainly work for you.